It starts by turning your process into something a team can actually build from.
Mapping the trigger. Pinning down the steps, the decision points, the rules the agent works to and the shape of the output. Working out where the agent's judgement should stop and a person's should start. The unglamorous detail that decides whether the finished agent is any good.
A specification precise enough to build from, and clear enough that you recognise your own process in it.